Organic light emitting diode and organic light emitting device including the same

ABSTRACT

Provided are an organic light-emitting diode (OLED) and an organic light-emitting device including the same. The OLED includes a first electrode, an organic emissive layer which includes a plurality of convex curves or a plurality of concave curves in a light-emitting region and of which a slope of an inclined plane of an upper region with respect to a horizontal line dividing a height of the plurality of convex curves into halves is greater than a slope of an inclined plane of a lower region thereof, and a second electrode provided on the organic emissive layer. Accordingly, the OLED and the organic light-emitting device including the same are capable of improving current efficiency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.16/898,041 filed on Jun. 10, 2020, which is a continuation applicationof U.S. patent application Ser. No. 16/505,489 filed on Jul. 8, 2019,which is a continuation application of U.S. patent application Ser. No.15/846,812 filed on Dec. 19, 2017, which claims the priority benefit ofKorean Patent Application No. 10-2016-0174658 filed in the Republic ofKorea on Dec. 20, 2016, all of which are hereby incorporated herein byreference in their entirety for all purposes as if fully set forthherein.

BACKGROUND Technical Field

The present disclosure relates to an organic light-emitting diode (OLED)and an organic light-emitting device including the same.

Discussion of the Related Art

Light emitted from an organic emissive layer of an organiclight-emitting device passes through various components of the organiclight-emitting device and is then discharged to the outside of theorganic light-emitting device. However, a part of the light emitted fromthe organic emissive layer may not be discharged to the outside of theorganic light-emitting device and becomes trapped inside the organiclight-emitting device, thereby decreasing light extraction efficiency ofthe organic light-emitting device.

In particular, in a bottom-emission type organic light-emitting deviceamong organic light-emitting devices, about 50% of light emitted from anorganic emissive layer is totally reflected from or absorbed by an anodeelectrode and is thus trapped inside the organic light-emitting device,and about 30% of the light emitted from the organic emissive layer istotally reflected from or absorbed by a substrate and is thus trappedinside the organic light-emitting device. As described above, about 80%of the light emitted from the organic emissive layer is trapped insidethe organic light-emitting device and only about 20% of the emittedlight is extracted to the outside. Therefore, luminous efficiency isvery low.

To improve the light extraction efficiency of the organic light-emittingdevice, a method of attaching a micro-lens array (MLA) to an outer sideof the substrate of the organic light-emitting device or a method offorming a micro-lens inside the organic light-emitting device has beensuggested.

However, even if the MLA is attached to the outer side of the substrateof the organic light-emitting device or the micro-lens is formed insidethe organic light-emitting device, a large amount of light is trappedinside the organic light-emitting device and thus the amount of thelight extracted to the outside is small. Furthermore, a part of lightincident from the substrate is reflected according to a state of apolarization axis of a polarizing plate due to the use of the MLA or themicro-lens. Accordingly, the reflectance (or diffuse reflectance) of theorganic light-emitting device may increase.

SUMMARY

Accordingly, embodiments of the present disclosure are directed to anorganic light emitting diode and an organic light emitting deviceincluding the same that substantially obviates one or more of theproblems due to limitations and disadvantages of the related art

An aspect of the present disclosure is to provide an organiclight-emitting diode (OLED) capable of decreasing reflectance and anorganic light-emitting device including the same.

Additional features and aspects will be set forth in the descriptionthat follows, and in part will be apparent from the description, or maybe learned by practice of the inventive concepts provided herein. Otherfeatures and aspects of the inventive concepts may be realized andattained by the structure particularly pointed out in the writtendescription, or derivable therefrom, and the claims hereof as well asthe appended drawings.

To achieve these and other aspects of the inventive concepts, asembodied and broadly described, an OLED and an organic light-emittingdevice having the same comprise a substrate divided into alight-emitting region and a non-light-emitting region. In oneembodiment, the OLED and the organic light-emitting device having thesame include an overcoat layer which is provided on the substrate andincludes a plurality of peak portions or a plurality of concave portionsin the light-emitting region and of which a slope of an inclined planeof the plurality of peak portions is greater than that of an inclinedplane of the plurality of concave portions. In one embodiment, the OLEDand the organic light-emitting device having the same include a firstelectrode provided on the overcoat layer. In one embodiment, the OLEDand the organic light-emitting device having the same include an organicemissive layer provided on the first electrode. In one embodiment, theOLED and the organic light-emitting device having the same include asecond electrode provided on the organic emissive layer.

According to one or more embodiments, an OLED and an organiclight-emitting device having the same include a substrate divided into alight-emitting region and a non-light-emitting region. In anotherembodiment, the OLED and the organic light-emitting device having thesame include an overcoat layer provided on the substrate. In anotherembodiment, the OLED and the organic light-emitting device having thesame include a first electrode provided on the overcoat layer. Inanother embodiment, the OLED and the organic light-emitting devicehaving the same include an organic emissive layer which is provided onthe first electrode and includes a plurality of convex curves or aplurality of concave curves in the light-emitting region and of which aslope of an inclined plane of the plurality of convex curves is greaterthan that of an inclined plane of the plurality of concave curves. Inanother embodiment, the OLED and the organic light-emitting devicehaving the same include a second electrode provided on the organicemissive layer and having a shape according to a shape of a top surfaceof the organic emissive layer.

According to one or more embodiments, an OLED and an organiclight-emitting device having the same include an organic emissive layerwhich is provided on a first electrode and includes a plurality ofconvex curves or a plurality of concave curves and of which a slope ofan inclined plane of an upper region with respect to a horizontal linedividing a height of the plurality of convex curves into halves isgreater than that of an inclined plane of a lower region thereof. Inanother embodiment, the OLED and the organic light-emitting devicehaving the same include a second electrode provided on the organicemissive layer.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the inventive concepts asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain various principles.

FIG. 1 is a cross-sectional view of an organic light-emitting displaydevice to which an embodiment is applied;

FIG. 2 is a plan view of an organic emissive layer in a region X of FIG.1;

FIG. 3 is an enlarged cross-sectional view of the region X of FIG. 1;

FIG. 4 is a conceptual diagram of variables determining a shape of peakportions of an overcoat layer;

FIG. 5 is a diagram illustrating variables determining a shape of peakportions of an overcoat layer of an organic light-emitting displaydevice according to an embodiment;

FIG. 6 is a conceptual diagram for explaining a gap in a micro-lensarray;

FIG. 7 is a diagram illustrating a light path at a maximum slopelocation on a peak portion according to an embodiment;

FIG. 8 is a diagram illustrating a shape of a peak portion of anovercoat layer according to a comparative example;

FIG. 9 is a graph showing current efficiency versus a shape of a peakportion of an overcoat layer; and

FIG. 10 is a graph showing a diffuse reflectance versus an aspect ratioA/R of a peak portion according to an embodiment.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the accompanying drawings. Embodiments set forthherein are provided as examples to sufficiently deliver the idea of thepresent disclosure to those of ordinary skill in the art. Thus, thepresent disclosure should not be construed as being limited to theseembodiments and may be embodied in many different forms. In thedrawings, the sizes, thicknesses, etc. of devices may be exaggerated forconvenience of explanation. Like reference numerals designate likeelements throughout.

Advantages and features of the present disclosure and methods ofachieving them will be apparent by referring to embodiments set forthherein in conjunction with the appended drawings. However, the presentdisclosure should not be construed as being limited to embodiments andmay be embodied in many different forms. Rather, these embodiments areprovided so that the present disclosure will be thorough and completeand will fully convey the concept of the present disclosure to those ofordinary skill in the art. The present disclosure should be defined byonly the scope of the claims. Like reference numerals designate likeelements throughout. In the drawings, the sizes of layers and regionsand the relative sizes thereof may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “above” or “on” another element or layer, the element or layer canbe directly on another element or layer or intervening elements orlayers. In contrast, when an element or layer is referred to as being“directly above” or “directly on” another element or layer, there are nointervening elements or layers present.

Spatially relative terms, such as “below”, “beneath”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe the relationship of one element or feature to anotherelement(s) or feature(s) as illustrated in the drawings. It will beunderstood that the spatially relative terms are intended to encompassdifferent orientations of each element in use or operation, in additionto the orientation depicted in the drawings. For example, if eachelement illustrated in the drawings is inverted, the element describedas “below” or “beneath” other elements would then be oriented “above”the other elements. Thus, the exemplary term “below” can encompass bothorientations of above and below.

When components of the present disclosure are described below, the terms“first,” “second,” “A,” “B,” “(a),” “(b),” and the like may be used.These terms are only used to distinguish one component from othercomponents. Thus, the essential features, order, sequence, or number ofthe components is not limited by these terms.

FIG. 1 is a cross-sectional view of an organic light-emitting displaydevice to which an embodiment is applied. Referring to FIG. 1, anorganic light-emitting display device 100 to which an embodiment isapplied includes a thin-film transistor (TFT) 120 including a gateelectrode 121, an active layer 122, a source electrode 123 and a drainelectrode 124; and an organic light-emitting diode (OLED) ELelectrically connected to the TFT 120, and including a first electrode150, an organic emissive layer 160 and a second electrode 170.

In detail, the gate electrode 121 is provided on a substrate 110. A gateinsulating layer 131 is provided on the gate electrode 121 and thesubstrate 110 to insulate the gate electrode 121 and the active layer122. The active layer 122 is provided on the gate insulating layer 131.An etch stopper 132 is provided on the active layer 122. The sourceelectrode 123 and the drain electrode 124 are provided on the activelayer 122 and the etch stopper 132. The source electrode 123 and thedrain electrode 124 are electrically connected to the active layer 122in such a manner so as to be in contact with the active layer 122, andare provided in a region of the etch stopper 132. Alternatively, theetch stopper 132 may not be provided.

For convenience of explanation, FIG. 1 illustrates only a driving TFTamong various TFTs applicable to the organic light-emitting displaydevice 100. Furthermore, although FIG. 1 illustrates that the TFT 120has an inverted staggered structure or a bottom gate structure, in whichthe gate electrode 121 is disposed opposite the source electrode 123 andthe drain electrode 124 with respect to the active layer 122, a TFThaving a coplanar structure or a top gate structure in which the gateelectrode 121 is located on the same side as the source electrode 123and the drain electrode 124 with respect to the active layer 122 is alsoavailable.

A passivation layer 133 is provided on the TFT 120. An overcoat layer140 is provided on the passivation layer 133.

Although not shown in FIG. 1, a color filter layer may be providedbetween the passivation layer 133 and the overcoat layer 140. The colorfilter layer may be provided at a location corresponding to alight-emitting region of the organic light-emitting display device 100.

The first electrode 150 of the OLED EL is provided on the overcoat layer140. A bank pattern 136 defining a light-emitting region and anon-light-emitting region is provided on portions of top surfaces of theovercoat layer 140 and the first electrode 150. The organic emissivelayer 160 and the second electrode 170 of the OLED EL are provided onthe first electrode 150 and the bank pattern 136.

The organic emissive layer 160 has a stacked structure (tandem white) ofa plurality of emissive layers to emit white light. The organic emissivelayer 160 may include a first organic emissive layer emitting bluelight, and a second organic emissive layer provided on the first organicemissive layer and emitting light having a color making white when mixedwith blue. The second organic emissive layer may be, for example, anorganic emissive layer emitting yellowish green light. Alternatively,the organic emissive layer 160 may include only an organic emissivelayer emitting blue, red, or green light.

Regions of the organic emissive layer 160 and the second electrode 170corresponding to the light-emitting region may have a plurality ofcurves including a plurality of convex curves 142 a or a plurality ofconcave curves 141 a. Alternatively, the region of each of the organicemissive layer 160 and the second electrode 170 corresponding to thelight-emitting region according to an embodiment may have at least onecurve among a plurality of convex curves and a plurality of concavecurves.

In this case, a slope of an inclined plane of the plurality of convexcurves 142 a of the organic emissive layer 160 may be greater than thatof an inclined plane of the plurality of concave curves 141 a thereof.Accordingly, each of regions of the organic emissive layer 160 may havean appropriate thickness and thus the current efficiency and lightextraction efficiency of the organic light-emitting display device 100may be improved. In detail, the plurality of convex curves 142 a of theorganic emissive layer 160 may be thinner than the plurality of concavecurves 141 a thereof.

In the OLED EL, the highest electric field is applied to a thinnestregion (a region corresponding to the plurality of convex curves 142 a)of the organic emissive layer 160 and thus major emission occurs in thisregion. That is, major emission may occur at the plurality of convexcurves 142 a of the organic emissive layer 160 of the OLED EL.

The thickness of each of the regions of the organic emissive layer 160may vary according to a shape of the organic emissive layer 160, inother words, a shape of the plurality of convex curves 142 a or theplurality of concave curves 141 a of the organic emissive layer 160. Forconvenience of explanation, embodiments will be described with respectto the shape of the plurality of convex curves 142 a of the organicemissive layer 160 below.

Variables which determine the shape of the plurality of convex curves142 a of the organic emissive layer 160 may include a diameter D1, aheight H1, an aspect ratio A/R1, a full width at half maximum F1, a fullwidth at half maximum aspect ratio F1_A/R1(=H/F), a slope S1, a halfheight aspect ratio-versus-aspect ratio Rm1 (ratio ofMLA=(F_A/R)/(A/R)), etc. of the plurality of convex curves 142 a of theorganic emissive layer 160.

The diameter D1 of the convex curves 142 a of the organic emissive layer160 refers to the distance between centers of two adjacent convex curves142 a. The height H1 of the convex curves 142 a of the organic emissivelayer 160 refers to a vertical length of the convex curves 142 a frombottom to top. The full width at half maximum F1 refers to a width ofthe convex curves 142 a at a half the height thereof as illustrated inFIG. 1. The aspect ratio A/R1 of the convex curves 142 a refers to avalue obtained by dividing the height H1 of the convex curves 142 a by aradius D1/2 of the convex curves 142 a.

In one embodiment, the diameter D1 of the convex curves 142 a of theorganic emissive layer 160 may be 1 μm to 5 μm, and the aspect ratioA/R1 of the convex curves 142 a may be 0.3 to 0.5. The full width athalf maximum F1 of the convex curves 142 a may be 0.975 μm to 1.5 μm.Thus, the full width at half maximum aspect ratio F1_A/R1(=H/F) of theconvex curve 142 a may be 0.4 to 0.75.

As described above, when the aspect ratio A/R1 of the convex curves 142a of the organic emissive layer 160 is 0.3 to 0.5, the full width athalf maximum aspect ratio F1_A/R1(=H/F) increases and thus a conditionthat the half height aspect ratio-versus-aspect ratio Rm1 should be 1.2or more is satisfied. The half height aspect ratio-versus-aspect ratioRm1 of the convex curves 142 a is a ratio between the full width at halfmaximum aspect ratio F1_A/R1 and the aspect ratio A/R1, and may be avariable which determines a region with the steepest maximum slope Smax.

Thus, in the organic light-emitting display device 100 according to anembodiment, the aspect ratio A/R1 of the convex curves 142 a of theorganic emissive layer 160 may be a small value of 0.3 to 0.5. Due tothe range of the aspect ratio A/R1 of the convex curves 142 a, the fullwidth at half maximum aspect ratio F1_AR1 may be 0.4 to 0.75.

Since the half height aspect ratio-versus-aspect ratio Rm1 is 1.2 ormore, a region with the maximum slope Smax of the organic emissive layer160 may correspond to the plurality of convex curves 142 a. The thinnestregion of the organic emissive layer 160 may be the region with themaximum slope Smax of the organic emissive layer 160. In other words, aregion of the organic emissive layer 160 including the plurality ofconvex curves 142 a may have the maximum slope Smax.

In another aspect, an upper region of the organic emissive layer 160with respect to a horizontal line dividing the height H1 of the convexcurves 142 a of the organic emissive layer 160 into halves may have themaximum slope Smax. A slope of an inclined plane of a lower region ofthe organic emissive layer 160 with respect to the horizontal linedividing the height H1 of the convex curves 142 a of the organicemissive layer 160 into halves may be less than that of an inclinedplane of the upper region.

An effective light-emitting region in which an electric field is locallyconcentrated may occur in a region of the organic emissive layer 160 ofwhich a slope of an inclined plane is great and which has a smallthickness at edges thereof between the first electrode 150 and thesecond electrode 170. In this case, when the OLED EL is driven, anelectric field is locally concentrated in the effective light-emittingregion and thus a main current path is formed. Thus, major emissionoccurs. In contrast, a region of the organic emissive layer 160corresponding to the plurality of concave curves 141 a may be anineffective light-emitting region of the OLED EL.

The maximum slope Smax of the plurality of convex curves 142 a of theorganic emissive layer 160 may be 20 to 60 degrees. Here, the maximumslope Smax of the organic emissive layer 160 refers to a maximum slopeangle between a tangent line of a bottom surface of the plurality ofconvex curves 142 a and a horizontal plane. When the maximum slope Smaxof the plurality of convex curves 142 a of the organic emissive layer160 is less than 20 degrees or greater than 60 degrees, a majorlight-emitting region of the OLED EL may change.

Similarly, the second electrode 170 of the OLED EL may have a pluralityof curves corresponding to those of the organic emissive layer 160.Thus, multiple reflection of light emitted from the OLED EL may occurand thus a large amount of light may be extracted outside the organiclight-emitting display device 100. Furthermore, the overcoat layer 140may have a plurality of peak portions or a plurality of concave portionscorresponding to the plurality of curves of the organic emissive layer160. That is, since the organic emissive layer 160 has the plurality ofcurves, the top surface of the overcoat layer 140 may have a shapeaccording to the morphology of the organic emissive layer 160.

Similarly, since the organic emissive layer 160 has the plurality ofcurves, the top surface of the first electrode 150 of the OLED EL mayhave a shape according to the morphology of the organic emissive layer160.

Although FIG. 1 illustrates that in the light-emitting region, the topsurfaces of the overcoat layer 140 and the first electrode 150 accordingto the present embodiment have shapes according to the morphology of theorganic emissive layer 160, the organic light-emitting display device100 according to an embodiment is not limited thereto, and at least oneof the overcoat layer 140 and the first electrode 150 may have a shapeaccording to the morphology of the organic emissive layer 160 in thelight-emitting region.

However, the shape of the organic light-emitting display device 100according to an embodiment is not limited to that illustrated in FIG. 1,provided that the organic emissive layer 160 and the second electrode170 each have a plurality of curves in the light-emitting region.

The organic light-emitting display device 100 according to an embodimentmay be a bottom emission type organic light-emitting display device, butembodiments of the present disclosure are not limited thereto and areapplicable to a top-emission organic light-emitting display device or adual emission type organic light-emitting display device if needed.

The above-described structure of the organic light-emitting displaydevice 100 will be described in detail with reference to FIGS. 2 and 3below. FIG. 2 is a plan view of an organic emissive layer in a region Xof FIG. 1. Referring to FIG. 2, in the light-emitting region, theorganic emissive layer 160 includes the plurality of convex curves 142 aand the plurality of concave curves 141 a. In this case, the pluralityof concave curves 141 a of the organic emissive layer 160 may have around shape when viewed from a plan view. The plurality of convex curves142 a of the organic emissive layer 160 may have a form surrounding theplurality of concave curves 141 a

However, the plurality of concave curves 141 a according to anembodiment are not limited to the round shape, and may have variousshapes such as a hemispherical shape, a semi-ellipsoidal shape, or apolygonal shape.

FIG. 3 is an enlarged cross-sectional view of the region X of FIG. 1.Referring to FIG. 3, the overcoat layer 140 according to an embodimentincludes a plurality of peak portions 142 and a plurality of concaveportions 141. The organic emissive layer 160 and the second electrode170 of the OLED EL formed on the overcoat layer 140 including theplurality of peak portions 142 and the plurality of concave portions 141may each have a shape according to the morphology of the overcoat layer140.

That is, a region of each of the organic emissive layer 160 and thesecond electrode 170 of the OLED EL corresponding to the region of theovercoat layer 140 including the plurality of peak portions 142 and theplurality of concave portions 141 may have a plurality of convex orconcave curves. Similarly, a region of the first electrode 150 of theOLED EL corresponding to the region of the overcoat layer 140 includingthe plurality of peak portions 142 and the plurality of concave portions141 may have a plurality of convex or concave curves.

When the organic emissive layer 160 of the OLED EL has the plurality ofconvex or concave curves, thicknesses of regions of the organic emissivelayer 160 in the light-emitting region may be different from each other.Here, the thicknesses of the regions of the organic emissive layer 160refer to vertical lengths thereof from a tangent line of the pluralityof convex or concave curves of the organic emissive layer 160 in regionsof the organic emissive layer 160 corresponding to the concave portions141 and the peak portions 142 of the overcoat layer 140.

In detail, a thickness d1 of a region A of the organic emissive layer160 between the peak portion 142 and the concave portion 141 of theovercoat layer 140 which is perpendicular to the first electrode 150,and a thickness d2 of a region B of the organic emissive layer 160corresponding to the peak portion 142 of the overcoat layer 140 may beless than a thickness d3 of a region of the organic emissive layer 160corresponding to the concave portion 141 of the overcoat layer 140.

For example, when the organic emissive layer 160 is formed according toa deposition method among various available methods, the organicemissive layer 160 deposited in a direction perpendicular to thesubstrate 110 may have a uniform thickness but may have a shapeaccording to the morphology of the overcoat layer 140.

According to features of a deposition process, a thickness of theorganic emissive layer 160 is smallest at a location at which theorganic emissive layer 160 has a largest slope. In detail, the organicemissive layer 160 has a smallest thickness in the regions A and B and aregion between the regions A and B of FIG. 3. Thus, in the OLED EL, ahighest electric field is applied to the thinnest region of the organicemissive layer 160 and major emission occurs in the thinnest region.

In other words, the thickness d1 of the region A of the organic emissivelayer 160 corresponding to a region 143 with a maximum slope Smax(hereinafter referred to as a ‘connection portion 143’) of the peakportion 142 of the overcoat layer 140 is less than the thicknesses d2and d3 of the regions of the organic emissive layer 160 respectivelycorresponding to the peak portion 142 and the concave portion 141 of theovercoat layer 140. Thus, major emission occurs in a region of the OLEDEL corresponding to the connection portion 143 of the overcoat layer140.

Although for convenience of explanation, a region with the maximum slopeSmax of the peak portion 142 is referred to as the connection portion143, the connection portion 143 may be a whole inclined plane of thepeak portion 142.

When the OLED EL has a micro-lens array to improve external lightextraction efficiency, convex curves occur on a surface of the OLED ELdue to the peak portions 142 of the overcoat layer 140 according tofeatures of a pattern of the micro-lens array as illustrated in FIG. 2.

In this case, in a region of the organic emissive layer 160 with a largeslope, the thickness d1 of an edge of the organic emissive layer 160between the first electrode 150 and the second electrode 170 is smalland thus an effective light-emitting region Y in which an electric fieldis locally concentrated, i.e., a region including the peak portion 142and the connection portion 143 of the overcoat layer 140, occurs.

In this case, when the OLED EL is driven, a main current path is formedand thus major emission occurs in the effective light-emitting region Ydue to local concentration of an electric field, whereas the concaveportion 141 of the overcoat layer 140 may be an ineffectivelight-emitting region Z.

In the light-emitting region of the organic light-emitting displaydevice 100 according to an embodiment, the overcoat layer 140 includes amicro-lens array pattern including the plurality of concave portions141, the plurality of peak portions 142 and the plurality of connectionportions 143.

Thus, an angle of a path of light which is emitted from the organicemissive layer 160 and which may be totally reflected and trapped insidethe first electrode 150 and the organic emissive layer 160 is changed tobe smaller than a total-reflection critical angle due to the micro-lensarray inserted into the overcoat layer 140, thereby increasing an amountof the light to be extracted outside the organic light-emitting displaydevice 100 and thus improving external luminous efficiency.

In this case, a propagation angle of the light emitted from the organicemissive layer 160 is changed by the inserted micro-lens array. Thepropagation angle of the light may become significantly different byeven a fine change in a shape of the micro-lens array.

As described above, a propagation angle of light may vary according tothe shape of the peak portions 142 of the overcoat layer 140, therebychanging external light extraction efficiency. That is, in the organiclight-emitting display device 100 according to an embodiment, a degreeto which light totally reflected and trapped inside the organic emissivelayer 160 is extracted to the outside may vary according to a light pathdepending on the shape of the peak portions 142 of the overcoat layer140 inserted to improve external light extraction efficiency.

As described above, a change in the light path according to the shape ofthe peak portions 142 or the concave portions 141 of the overcoat layer140 inserted to improve the external light extraction efficiency may bea major factor improving light extraction efficiency. For convenience ofexplanation, variables determining the shape of the peak portions 142 ofthe overcoat layer 140 will be described below.

Variables which determine the convex portions of the overcoat layer 140may include a diameter D, a height H, an aspect ratio A/R, a full widthat half maximum F, a full width at half maximum aspect ratio F_A/R(=H/F), a slope S, a gap G between bottoms of two adjacent peak portions142, a half height aspect ratio-versus-aspect ratio Rm (ratio ofMLA=(F_A/R)/(A/R)), etc. of the peak portions 142 of the overcoat layer140.

FIG. 4 is a conceptual diagram of variables determining the shape of apeak portion of an overcoat layer. FIG. 5 is a diagram illustratingvariables determining a shape of a peak portion of an overcoat layer ofan organic light-emitting display device according to an embodiment.FIG. 6 is a conceptual diagram for explaining a gap G in a micro-lensarray.

Referring to FIGS. 4 and 5, the diameter D of the peak portions 142 ofthe overcoat layer 140 refers to the distance between centers of twoadjacent peak portions 142. The height H of the peak portions 142 of theovercoat layer 140 refers to a vertical length from the bottom of theconcave portions 141 to the top of the peak portions 142. The full widthat half maximum F refers to a width of the peak portions 142 at a halfthe height H as illustrated in FIG. 4. The aspect ratio A/R of the peakportions 142 refers to a value obtained by dividing the height H of thepeak portions 142 by a radius D/2 of the peak portions 142.

In one embodiment, the diameter D of the peak portions 142 of theovercoat layer 140 may be 1 μm to 5 μm, and the height H thereof may be0.6 μm to 1.3 μm. When the diameter D and the height H of the peakportions 142 are in the above-described ranges, the aspect ratio A/R ofthe peak portions 142 may be in a range of 0.24 to 2.6, and preferably,a range of 0.3 to 0.5. The full width at half maximum F of the peakportions 142 may be 0.975 μm to 1.5 μm. Thus, the full width at halfmaximum aspect ratio F_A/R of the peak portions 142 may be 0.4 to 0.75.

As described above, when the aspect ratio A/R of the peak portions 142of the overcoat layer 140 is 0.3 to 0.5, the full width at half maximumaspect ratio F_A/R may increase and thus a condition that the halfheight aspect ratio-versus-aspect ratio Rm should be 1.2 or more may besatisfied. The half height aspect ratio-versus-aspect ratio Rm of thepeak portions 142 is a ratio between the full width at half maximumaspect ratio F_A/R and the aspect ratio A/R and may be thus a variabledetermining a region with a steepest maximum slope Smax.

Thus, in the organic light-emitting display device 100 according to anembodiment, the aspect ratio A/R of the peak portions 142 of theovercoat layer 140 may be a low value ranging from 0.3 to 0.5. Due tothe range of the aspect ratio A/R of the peak portions 142, the fullwidth at half maximum aspect ratio F_A/R may be 0.4 to 0.75. A surfaceof the organic light-emitting display device 100 according to anembodiment on which the OLED EL is located may be a top surface of theovercoat layer 140 having the peak portions 142 satisfying theabove-described condition.

By forming the peak portions 142 of the overcoat layer 140 to satisfythe above-described condition, an increase rate in current efficiency ofthe organic light-emitting display device 100 may be higher than that incurrent efficiency of an organic light-emitting display device includingthe peak portions 142 which are not in the above-described ranges, aswill be described in detail with reference to FIGS. 8 and 9 below.

If only the aspect ratio A/R is applied as a variable defining the shapeof the peak portions 142 of the overcoat layer 140, the shape of thepeak portions 142 of the overcoat layer 140 may change when valuesdefined by the other variables such as the full width at half maximum Fand the gap G between the bottoms of two adjacent peak portions 142 arechanged, although the aspect ratio A/R is the same and thus ratiosdefined only by the diameter D and the height H are the same.

The overcoat layer 140 having the peak portions 142 which are in theabove-described ranges will be described in detail below. FIG. 7 is adiagram illustrating a light path at a maximum slope location on a peakportion according to the present embodiment.

Referring to FIG. 7, the peak portion 142 of the overcoat layer 140includes a second region A with the maximum slope Smax. In detail, whenthe peak portion 142 of the overcoat layer 140 is divided into halveswith respect to the height H thereof, the peak portion 142 may bedivided into a first region B adjacent to the concave portion 141 andthe second region A farther from the concave portion 141 than the firstregion B. In one embodiment, the second region A of the peak portion 142may have the maximum slope Smax. In other words, an upper region of thepeak portion 142 is the second region A with the maximum slope Smax withrespect to a horizontal line dividing a height of the peak portion 142into halves, and a lower region of the peak portion 142 is the firstregion B with a slope less than that of the second region A.

As described above with reference to FIG. 4, the half height aspectratio-versus-aspect ratio Rm of the peak portion 142 according to anembodiment may be 1.2 or more. Furthermore, referring to FIGS. 4 and 7,when the half height aspect ratio-versus-aspect ratio Rm of the peakportion 142 is less than 1.2, the first region B is a region with themaximum slope Smax of the peak portion 142. When the half height aspectratio-versus-aspect ratio Rm of the peak portion 142 is 1.2 or more, thesecond region A is a region with the maximum slope Smax.

In other words, since the half height aspect ratio-versus-aspect ratioRm of the peak portion 142 according to an embodiment is less than 1.2or more, the region A may be a region with the maximum slope Smax.

Alternatively, a whole inclined plane of the peak portion 142 of theovercoat layer 140 may have the maximum slope Smax. That is, a slope ofthe concave portion 141 of the overcoat layer 140 according to anembodiment may be less than the slope S of the peak portion 142.

Accordingly, as illustrated in FIG. 7, the micro-lens array of theovercoat layer 140 has a shape of which a slope of the inclined planeincreases from the concave portion 141 to the peak portion 142, and maythus taper from the concave portion 141 to the peak portion 142.

In this case, as illustrated in FIG. 4, the slope S of the peak portion142 is understood to mean an angle between a tangent line of the bottomsurface of the peak portion 142 and a horizontal plane. The maximumslope Smax may be understood to mean a maximum angle between the tangentline of the bottom surface of the peak portion 142 and the horizontalplane. Here, the slope S of the peak portion 142 may be 20 to 60degrees. When the slope S of the peak portion 142 is not in theabove-described range, the amount of light extracted through theovercoat layer 140 may decrease.

Thus, as illustrated in FIG. 3, a region of the organic emissive layer160 located on the overcoat layer 140 and corresponding to the secondregion A with the maximum slope Smax of the peak portion 142 may bethinnest. The thickness of the organic emissive layer 160 refers to alength of a region of the organic emissive layer 160 corresponding tothe second region A with the maximum slope Smax of the peak portion 142and perpendicular to a tangent line of a curve of the organic emissivelayer 160. Thus, an electric field is concentrated in the region of theorganic emissive layer 160 corresponding to the peak portion 142 of theovercoat layer 140 and thus the OLED EL may exhibit maximum luminousefficiency.

Furthermore, as illustrated in FIG. 7, the peak portion 142 of theovercoat layer 140 has a tapered shape and thus a light path in alateral direction may decrease, thereby improving external lightextraction efficiency. That is, in the organic light-emitting displaydevice 100 according to an embodiment, a region of the OLED ELcorresponding to the peak portion 142 of the layer 140 has maximumluminous efficiency, and light extraction efficiency at the peak portion142 of the overcoat layer 140 is high.

Although the aspect ratios A/R of the peak portions 142 of the overcoatlayer 140 are substantially the same, the peak portions 142 may havevarious shapes. For example, even if a peak portion has the same orsubstantially the same aspect ratio A/R as the peak portion 142 of theovercoat layer 140 according to an embodiment, the peak portion may havea plump shape unlike the shape of the peak portion 142 according to thepresent embodiment. In detail, even if a peak portion has the same orsubstantially the same aspect ratio A/R as the peak portion 142according to the present embodiment, a change in the full width at halfmaximum F of the peak portion 142 may result in a change in a shape ofthe peak portion, as will be described in detail with reference to FIG.8 below.

FIG. 8 is a diagram illustrating a shape of a peak portion of anovercoat layer according to a comparative example. Referring to FIG. 8,an aspect ratio A/R of a peak portion 242 of an overcoat layer 240according to the comparative example may be the same or substantiallythe same as that of the peak portion 142 of the overcoat layer 140according to the present embodiment illustrated in FIG. 7.

In contrast, a full width at half maximum F′ of the peak portion 242 ofthe overcoat layer 240 according to the comparative example may begreater than the full width at half maximum F of the peak portion 142 ofthe overcoat layer 140 according to an embodiment illustrated in FIG. 7.In this case, a region with a maximum slope Smax of the peak portion 242of the overcoat layer 240 according to the comparative example islocated more adjacent to a concave portion 241 than the region with themaximum slope Smax of the peak portion 142 of the overcoat layer 140according to the present embodiment.

Thus, a propagation path of light emitted from the OLED EL on theovercoat layer 140 may be different from that of light emitted from anOLED on the overcoat layer 240. In detail, major emission occurs in aregion of the OLED corresponding to the region with the maximum slopeSmax of the overcoat layer 140 or 240, and a path in which light emittedfrom the region of the OLED is extracted to the outside varies accordingto the shape of the peak portion 142 or 242 of the overcoat layer 140 or240.

As illustrated in FIG. 8, a part of light emitted from a region of theovercoat layer 240 according to the comparative example corresponding tothe region with the maximum slope Smax is extracted to the outside of asubstrate while colliding against a side of a region having maximumslope Smax of the overcoat layer 240, but the remaining light is notextracted to the outside of the substrate and is trapped inside. Thatis, light extraction efficiency according to the comparative example islow.

In contrast, as illustrated in FIG. 7, a large amount of light emittedfrom the region of the overcoat layer 140 corresponding to the regionwith the maximum slope Smax collides against a side of the region withthe maximum slope Smax and is thus extracted to the outside of thesubstrate. That is, in the present embodiment, light extractionefficiency may be improved.

Next, current efficiencies according to an embodiment and a comparativeexample will be described with reference to FIG. 9 below. FIG. 9 is agraph showing current efficiency versus a shape of a peak portion of anovercoat layer.

Referring to FIG. 9, when an aspect ratio A/R of a peak portion is 0.5or less, current efficiency of an organic light-emitting display deviceaccording to an embodiment is higher than that of an organiclight-emitting display device according to a comparative example (seeFIG. 8). That is, even if aspect ratios A/R of overcoat layers accordingto the present embodiment and the comparative example are the same orsubstantially the same, it can be seen that as full widths at halfmaximum F of the peak portions of the overcoat layers decrease, thecurrent efficiencies according to the present embodiment and thecomparative example are different. In particular, when an overcoat layeraccording to an embodiment is applied to a display device, currentefficiency may be more improved. This means when a thin organic emissivelayer is stacked on a peak portion according to an embodiment, an OLEDmay have an optimum structure and thus current efficiency may be moreimproved.

On the other hand, the aspect ratio A/R of the peak portion isproportional to diffuse reflectance of a panel. That is, an increase inthe aspect ratio A/R of the peak portion results in an increase in thediffuse reflectance. Here, the diffuse reflectance refers to thereflectance of a display device improved when a part of light incidentfrom the substrate is reflected in the same state as a polarization axisof a polarizing plate. Even when the diffuse reflectance is high, whencurrent efficiency is high, black luminosity of an organiclight-emitting display device may be degraded.

Therefore, there is a need for a structure capable of decreasing diffusereflectance and having improved current efficiency. A structureaccording to an embodiment may satisfy this need as will be describedwith reference to FIG. 10 below. FIG. 10 is a graph showing a diffusereflectance versus an aspect ratio A/R of a peak portion according to anembodiment.

Referring to FIG. 10, in a structure having a peak portion according toan embodiment, the diffuse reflectance increases when the aspect ratioA/R of the peak portion increases. On the other hand, when the diffusereflectance of a panel into which a micro-lens array is inserted isabout 20% or less, a viewer may not be able to recognize that blackluminosity has been degraded. The diffuse reflectance of an organiclight-emitting display device having a peak portion according to anembodiment is about 20% or less when an aspect ratio A/R thereof is lessthan 0.6.

That is, referring to results shown in the graphs of FIGS. 9 and 10, theorganic light-emitting display device having the peak portion accordingto the present embodiment has high current efficiency and low diffusereflectance when the aspect ratio A/R of the peak portion is 0.5 orless.

As described above, since a slope of an inclined plane of a peak portionof an overcoat layer according to an embodiment is greater than that ofa concave portion of the overcoat layer, major emission may occur in aregion of an OLED corresponding to the peak portion. Thus, currentefficiency may be increased, light extraction efficiency may beimproved, and low diffuse reflectance may be obtained.

In an OLED and an organic light-emitting device including the sameaccording to embodiments, in a light-emitting region, a slope of aninclined plane of peak portions of an overcoat layer is greater thanthat of an inclined plane of concave portions of the overcoat layer,thereby decreasing reflectance and improving current efficiency.

While an OLED applicable to an organic light-emitting display deviceaccording to an embodiment has been described above, embodiments are notlimited thereto. The OLED according to an embodiment may be used aloneor applied to an organic light-emitting device, such as an illuminationdevice with an OLED, and the like.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the organic light emittingdiode and the organic light emitting device including the same of thepresent disclosure without departing from the technical idea or scope ofthe disclosure. Thus, it is intended that the present disclosure coverthe modifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

What is claimed is:
 1. An organic light-emitting diode, comprising: anovercoat layer having at least one concave portion and at least oneconnection portion; a first electrode on the overcoat layer; an organicemissive layer on the first electrode and having at least one convexcurve, wherein a thickness of the organic emissive layer correspondingto the at least one connection portion is smaller than a thickness ofthe organic emissive layer corresponding to the at least one concaveportion, and a second electrode on the organic emissive layer.
 2. Theorganic light-emitting diode of claim 1, wherein the overcoat layerfurther includes at least one peak portion to constitute a micro-lensarray pattern.
 3. The organic light-emitting diode of claim 2, wherein athickness of the organic emissive layer corresponding to the at leastone peak portion is smaller than a thickness of the organic emissivelayer corresponding to the at least one concave portion.
 4. The organiclight-emitting diode of claim 3, wherein a thickness of the organicemissive layer corresponding to the at least one connection portion issmaller than a thickness of the organic emissive layer corresponding tothe at least one peak portion.
 5. The organic light-emitting diode ofclaim 2, further comprising a bank pattern on the overcoat layer,wherein the bank pattern overlays an edge of the at least one peakportion.
 6. The organic light-emitting diode of claim 2, wherein the atleast one concave portion is arranged in a line along a first directionand are staggered along a second direction.
 7. The organiclight-emitting diode of claim 1, wherein the organic emissive layer hasa stacked structure of a plurality of emissive layers to emit a whitelight.
 8. The organic light-emitting diode of claim 1, wherein a slopeof an inclined plane of an upper region of the organic emissive layerwith respect to a horizontal line dividing a height of the plurality ofconvex curves into halves is greater than a slope of an inclined planeof a lower region of the organic emissive layer.
 9. The organiclight-emitting diode of claim 1, wherein a slope of an inclined plane ofthe organic emissive layer corresponding to the at least one connectionportion is greater than a slope of an inclined plane of the organicemissive layer corresponding to the at least one concave portion. 10.The organic light-emitting diode of claim 1, wherein an amount of alight emitted from an inclined plane of the organic emissive layercorresponding to the at least one connection portion is greater than anamount of a light emitted from an inclined plane of the organic emissivelayer corresponding to the at least one concave portion.
 11. The organiclight-emitting diode of claim 1, wherein the organic emissive layerfurther includes at least one concave curve, wherein the at least oneconcave curve has a round shape, and wherein the at least one convexcurves surround the at least one concave curve.
 12. The organiclight-emitting diode of claim 1, further comprising: a bank pattern onthe overcoat layer; and a color filter layer under the overcoat layer.13. An organic light-emitting device, comprising: a substrate; a thinfilm transistor on the substrate; a passivation layer on the thin filmtransistor; an overcoat layer on the passivation layer, the overcoatlayer having at least one concave portion and at least one connectionportion; a first electrode on the overcoat layer; an organic emissivelayer on the first electrode and having at least one convex curve,wherein a thickness of the organic emissive layer corresponding to theat least one connection portion is smaller than a thickness of theorganic emissive corresponding to the at least one concave portion; anda second electrode on the organic emissive layer.
 14. The organiclight-emitting device of claim 13, wherein the overcoat layer furtherincludes at least one peak portion to constitute a micro-lens arraypattern.
 15. The organic light-emitting diode of claim 14, wherein athickness of the organic emissive layer corresponding to the at leastone peak portion is smaller than a thickness of the organic emissivelayer corresponding to the at least one concave portion.
 16. The organiclight-emitting diode of claim 15, wherein a thickness of the organicemissive layer corresponding to the at least one connection portion issmaller than a thickness of the organic emissive layer corresponding tothe at least one peak portion.
 17. The organic light-emitting diode ofclaim 13, wherein the organic emissive layer has a stacked structure ofa plurality of emissive layers to emit a white light.
 18. The organiclight-emitting diode of claim 13, wherein a slope of an inclined planeof an upper region of the organic emissive layer with respect to ahorizontal line dividing a height of the plurality of convex curves intohalves is greater than a slope of an inclined plane of a lower region ofthe organic emissive layer.
 19. The organic light-emitting diode ofclaim 13, wherein a slope of an inclined plane of the organic emissivelayer corresponding to the at least one connection portion is greaterthan a slope of an inclined plane of the organic emissive layercorresponding to the at least one concave portion.
 20. The organiclight-emitting diode of claim 13, wherein the organic emissive layerfurther includes at least one concave curve, wherein the at least oneconcave curve has a round shape, and wherein the at least one convexcurves surround the at least one concave curve.